Sound recording and reproducing mechanism



July 14, 1942.

T. LIINDENBERG, JR SOUND RECORDING AND REPODUCING MEGHANISM Filed sept'. .12, 195s `Patentedy July 14, 1942 SOUND RECORDING AND REPRODUCING MECHANI Theodore Lindenberg, Jr., Columbus, Ohio Application September 12, 1938, Serial No. 229,453

8 Claims.

This invention relates generally to electrically actuated sound reproducing mechanism and is particularly directed to an improved translating device commonly designated as a pickup mechanis'm. These devices are usually carried by the outer end of a tone arm and are equipped with a needle which engages the sound track of a phonograph record. They transform the needle vibrations caused by the irregularities in the sound track to electrical impulses which are then amplified and changed by suitable apparatus into audible sounds.

'I'he primary object of the invention resides in the provision of a pickup device having a light weight record engaging element which is super-v sensitive and will respond to vibrations of very high as well as very low frequencies.

Another object of the invention is to provide an electrical pickup having a record engaging element with high wear resisting qualities in order that it will last indefinitely. This provision will permit the permanent attachment 4of this element to the pickup device, thus eliminating the necessity of providing a set screw to hold it in place together with its attendant weight.

It is also an object of the invention to provide a supporting device for the record engaging member and to provide a flexible mounting for the supporting device whereby it will ilex or move in a single plane disposed at right angles to the sound track on the record. The supporting device will be provided with suitable mechanism to translate the vibrations transmitted thereto by the record into electrical impulses. l

A further object of the invention resides in providing a pickup with a permanent magnet, the'ends of which engage pole pieces, The latter members extend toward one another and terminate in spaced relation, there being a supporting element for a record engaging member positioned between the spaced ends of the pole pieces. This supporting element is to be formed oi nonmagnetic material and is to have a light weight magnetic responsive device carried by its upper end.

It is also an object of the invention to provide improved means for supporting the non-magnetic element which in turn supports the record engaging member.

With vthese and other objects in view which will appear as the description proceeds, the invention resides in the novel construction of eiements and their particular location as pointedv out in the following description of one form of 55 the invention illustrated in detail in the accompanying drawing. In the drawing: v

Fig. 1 is a vertical longitudinal sectional view taken through the 'outer end of a tone arm equipped with a pickup formed in accordance with the present invention;

Fis'. 2 is a vertical transverse sectional view taken through the pickup device on the plane indicated by the line II-II of Fig. 1;

Fig. 3 is a horizontal sectional view taken on the plane indicated by the line III-III of Fig. 2;

Fig. 4 is a detail' longitudinal sectional view taken through the member which supports the record engaging element;

Fig. 5 is a perspective view of the upper portion of the member shown in Fig. 4, together with the members used in flexibly supporting it.

Referring more particularly to the drawing,A

the numeral l designates the outer portionof the tone arm of an electrical sound reproducing machine. Secured to the outer end of the arm I is a metallic head 2 which front face 3 to which the pickup mechanism 4 5 issecured. This pickup mechanism comprises a horseshoe shaped magnet 5 secured flatwise to the face 3. The ends of the magnet 5are bifurcated as at 6 for the reception ofthe end portions of pole pieces l and 8. The latter members have slotted openings formed in the ends adjacent the magnet for the' reception of bolts y9 used to secure the magnet in connection with the head 2. The openings in the pole pieces are slotted to provide for their adjustment laterally with respect to the magnet.v The opposite ends of the pole pieces extend toward one another and terminate in spaced relation near the center of the supporting head 2. The adjacent ends of the pole pieces are beveled as at I0 to permit them to enter recesses formed in anchor blocks II and I2 which are also secured to the face of the' supporting head 2. The blocks II and I2 have flat surfaces engaging one another on a plane at right angles to the longitudinal axis of the pole pieces. l

Positioned between these dat surfaces o1' thc blocks is a pair of vanes I3 formed of a tough fibrous substance, these vanes being securely clamped between the blocks and having their inner ends projecting into the recess between the pole pieces. The inner ends of the vanos are cemented to the outer surface of a coil of wire I 4 which is wound around the square upper end of a hollow brass tube I5. The wire of the .coil isA `of small diameter and is enameled to inis provided with a ilat comprising a reproducer arm sulate the convolutions from one another. The coil is also impregnated with cellulose cement to securely unite it with the upper end of the tube I5 and with the inner ends of the vanes I3. The upper end of the tube I5 is closed by means of a plug I6 to prevent the collapse of the tube in the event the outer end should be struck while the pickup device is being handled.

By reason of the above described method of mounting the tube I5, it will be free to'iiex in a plane transverse to that of the vanes by which it is supported. The-plane in which the tube iiexes will be parallel to the plane o! thesurface of the supporting head 2. This provision makes the pickup adaptable to laterally cut sound tracks. The coil surrounding the upper end of the tube is energized by the magnetic forces of the magnet and to prevent it from being injured Y by contact with the pole pieces, there is provided at the sides of the squared end of the tube not in engagement with the vanes, rubber damping pads I1. The pole pieces are adjusted toward the tube until the inner ends engage the rubber pads and lightly but rmly support the tube midway therebetween.

The lower end of the tube is provided with an inwardly directed houlder I8 against which the upper portion Vof a diamond is positioned. The lower edge of the tube is then rolled around the shoulder on the diamond to -secure it in position in the lower end of the tube. The lower end of the diamond is sharpened to provide a rounded point I9 for engagement with the sound track of the records to be reproduced.

The en'ds of the coil I4 pass through an opening in the supporting head 2 and through the tone arm to amplifying apparatus, not shown. A cover formed of sheet metal or similar material is secured to the supporting head 2 and encloses the pickup device to prevent the accumulation of dirt or otherforeign matter thereon.

In use, the diamond point I9 is positioned in the sound track of a phonograph record. As the record revolves, the sound track passes the lower end of the point which will be vibrated laterally by the irregularities of the sound track. This lateral vibration causes a flexing of the vanes |3` and the coil I4 is oscillated in the magnetic iield between the pole pieces. This movement sets up electrical impulses in the coil which are transmitted to the amplifying mechanism where translation is made into audible sounds.

While I have shown and described an improved pickup device, numerous variations therein are contemplated and it is my desire to protect these various modifications by .the iollowing claims. v

What is claimed is:

1. In sound reproducing mechanism, a pickup having an enlarged head at the outer end thereof, a permanent horseshoe magnet secured to said head, an anchor block positioned on said head between the spaced ends of said magnet, a non-magnetic tube, a record-engaging stylus carried by one end of said tube, a coil of wire carried by the opposite end of said tube, means for flexibly connectl ing the latter end of said tube to said anchor block, a pole piece extending from each end of said magnet to a point adjacent said coil, and a resilient block positioned between said coil and each of said pole pieces.

2. In sound reproducing apparatus, a pickup device comprising a support, a horseshoe magnet secured to the front face of said support, a pole piece engaging each end of said magnet, the free ends of said pole pieces projecting toward one another and terminating in spaced relation, a tubular non-magnetic member having one end positioned between the ends of said pole pieces, a. record engaging point carried by the opposite end of said tubular member, a coil of wiresur.- rounding the end of the tubular member between said pole pieces. a iiexible vane extending radially from opposite sides of said tubular member, and an anchor block secured to said support, said anchor block engaging the outer portions of said flexible vanes to support said tubular member for movement in a plane parallel to the front face of said support.

3. In sound reproducing mechanism, a pickup device comprising a support, an inverted U- shaped magnet e cured to said support, pole pieces each having one end in engagement with an end of said magnet, the other ends of said pole pieces projecting toward one another and terminating in spaced relation, a pair of anchor blocks secured to said support, a pair of iiexible vanes each having one end clamped between said blocks, a tubular non-magnetic member supported at one'end by the relatively adjacent ends of said vanes, the supported end of said tubular member being disposed between the spaced ends of said pole pieces, a coil of wire surrounding the end of said tubular member between said pole pieces, and a record engaging wear resisting stylus secured to the free end of said tubular member.

4i Vibration translating apparatus for phonographs comprising an oscillatory stylus having a needle point adapted to follow the groove of a phonographic record, a coil of an electrical conducting material attached to the stylus in spaced relation from its needle point, said coil oscillating mechanically in unison with the stylus, a source of constant magnetic flux in which said coil is disposed, aligned fibrous vanes supporting 'said stylus for oscillation in a single plane,

and compressible resilient means carried by said source of magnetic iiux and disposed in the plane of oscillation of the stylus.

5. Vibration translating apparatus for phonographs comprising a record-engaging needle point at one end, a coil of an electrical conducting material rigidly connected with the stylus in spaced relation from the needle point end thereof, a pair of pole pieces spaced to produce betweentheir adjacent ends a gap for the establishment of magnetic uX, the coil of said stylus being disposed in said gap, means pivotally mounting the stylus for oscillation about a single axis transversely intersecting said gap, and

, resilient compressible means arranged between said stylus and said pole pieces and disposed in the plane of oscillation of the stylus.

6. Vibration translating apparatus for phonographs comprising a swinging reproducer arm having its outer end formed with an enlarged head, a magnet having opposed pole pieces with the complemental ends of said pieces relatively spaced to produce a magnetic flux gap, a stylus formed with a record groove-engaging needle point at one end, the other end of said stylus terminating in said gap, a coil of an electrical conducting material rigidly connected with said stylus in registration with said flux gap, aligned and opposed torsion strips having their inner ends secured to said stylus and their outer ends stationarily fastened in commotion with the head of said reproducer arm, said strips providing for the oscillation of said stylus in a. single plane, and resilient members arranged in said gap and interposed between the complementa] ends of said pole pieces and stylus, said resilient members being arranged in the plane of oscillation of said stylus and substantially at, right angles to the plane of said strips.

7. Vibration translating apparatus for phono-A ends fastened to a stationary support, said strips permittingof oscillation of said stylus in a single plane.

8. A stylus for phonographic vibration translating apparatus comprising a light weight body having a record-engaging needle point formed at one end thereof, the opposite end of said body being formed with polygonal sides, a coil of an Velectrical conducting material surrounding the polygonal sides of said stylus and stationarily secured thereto, and a pair of aligned torsion strips extending from opposite sides of the polygonal end of said stylus, the relatively adjacent ends of said strips being rigidly bonded to said stylus.

THEODORE LINDENBERG, JR. 

